The present invention relates to health care, or patient care, equipment. In particular, the present invention relates to an apparatus for recovering waste gas from a patient""s exhalations in a post-anaesthesia care unit.
Anaesthetic gases are commonly given to patients undergoing surgery. As is well known, overexposure to anaesthetic and analgesic gases, such as nitrous oxide, halothane, enflurane, isoflurane, desflurane and sevoflurane, poses serious health risks to health care workers. Both short term and long term exposure to anaesthetic gases can adversely affect performance, cognition, audiovisual ability and dexterity among health care workers. To mitigate the recognized health risks to medical personnel, recommended exposure limits have been established by government agencies, such as the U.S. Department of Health and Human Services.
The anaesthetics gases are typically administered to an intubated patient through the use of a tracheal tube that is attached to a closed scavenging circuit. The patient inhales an anaesthetic gas mixture, and exhales residual unmetabolized anaesthetic gases. Nitrous oxide (N2O), which is commonly used as a carrier for other anaesthetic gases, is the most prevalent compound in the exhaled gases because it is not metabolized in the body and is excreted with each exhalation by the patient. In the closed anaesthetic system used in an operating room, the scavenging circuit limits the exposure of surgical staff. However, once the surgery is completed, the patient is extubated and left to recover in a post anaesthesia care unit. In the post anaesthesia care unit, the patient continues to expel anaesthetic gases, or xe2x80x9coff-gasxe2x80x9d for a period of time, generally 20-30 minutes. As a result, if several patients are recovering in a post anaesthesia care unit, the level of nitrous oxide and other anaesthetic gases can quickly exceed the recommended time averaged exposure limit, currently 25 parts per million (ppm) in the United States.
To deal with this problem, hospitals and other surgical centers require an efficient and cost effective method of handling the contamination of post anaesthesia care units that reduces the risk to medical workers without risking patient health.
Canadian Patent No. 1,259,872 to Lindkvist discloses a gas collecting device in the form of a double-walled, hollow, cup-shaped mask that fits around a patient""s chin. The device is attached to a suction system which draws away a portion of the patient""s exhalations. This device is intended for the administration of anaesthesia in a dental office, where it is necessary for the dentist to work in the mouth cavity. Since it does not cover the patient""s nose and mouth, a large portion of the anaesthetic gases are still expelled directly into the atmosphere. Further, the device is large, bulky and semi-rigid material which could possibly injure an unconscious patient.
U.S. Pat. No. 5,474,060 to Evans discloses a face mask for administering a gas to a patient and monitoring the patient""s exhalations for oxygen and carbon dioxide levels. By and large, the air exhaled by the patient is exhausted through conventional side vents. However, a portion of the exhaled air is diverted and sampled through a tube attached to a sampling unit. This device permits the controlled administration of oxygen, which is often required by patients post-anaesthesia, but does not address the problem of recovering anaesthetic gases off-gassed by the patient.
U.S. Pat. No. 5,676,133 to Hickle et al. discloses a post-operative anaesthesia recovery system. The system includes a face mask that is attached to an oxygen supply and a scavenging unit. The system is closed, and is intended to recover all the air exhaled by the patient, and is essentially a post-operative version of the scavenging system used in an operating room. Because this system is fully sealed, it requires a number of specialized adapters and valves to permit the patient to inhale and exhale without undue effort. The patient""s breathing must also be constantly monitored to ensure that breathing remains normal. As a result, this system is not cost effective in most post-anaesthesia units.
It is therefore desirable to provide an apparatus for removing anaesthesia gases exhaled by a patient in a post-anaesthesia care unit that overcomes the limitations of the prior art. In particular, it is desirable that such an apparatus maintain the level of anaesthetic gases in a post-anaesthesia care unit to within suggested limits, permit a patient to be administered oxygen, allow normal breathing by the patient. The apparatus should also be relatively inexpensive, and simple to install in existing post-operative anaesthesia units.
In a first embodiment according to the present invention, there is provided a post-operative gas recovery apparatus, comprising:
a mask for sealingly engaging a patient""s face to capture waste anaesthetic gases exhaled by a patient, the mask including a recovery port in fluid communication with an evacuation assembly for drawing the waste anaesthetic gases to a discharge assembly, and an oxygen port for communicating with an oxygen source for providing oxygen to the patient;
an air entrainment cartridge interconnecting the evacuation assembly and the recovery port to permit fluid communication therebetween, the air entrainment cartridge including entrainment means permitting a flow of atmospheric air to enter the apparatus to provide a pressure inside the mask that allows the patient to breathe in a conventional manner.
In a further embodiment according to the present invention there is provided an air entrainment cartridge for a post-operative gas recovery apparatus, comprising:
a hollow tube having a distal end for attaching to a recovery port of a mask; a proximal end for attaching to an evacuation assembly; and air entrainment means for permitting a flow of atmospheric air to be entrained within the tube.
In a preferred embodiment of the present invention, the air entrainment means are channels formed on the outside of the air entrainment cartridge. The channels are incised longitudinally into the cartridge, and are only partially covered by tubing leading to a blower unit.